Field of the Invention
The present invention relates to a pressure-resistant glass sphere capable of being used for exploration and searching in the deep sea, the ocean floor, the underground, the thick ice of the Antarctic Continent or the like by housing observation apparatuses and measurement apparatuses or the like such as a camera, a video camera and a seismometer in the pressure-resistant glass sphere.
Description of Related Art
In order to explore and search the deep sea, the ocean floor, the underground, the thick ice of the Antarctic Continent or the like by using the camera, the video camera, the seismometer or the like, a pressure-resistant container for storing the observation apparatuses and the measurement apparatuses is required. Conventionally, high strength metal material such as Titanium alloy is used.
More recently, a pressure-resistant container made of glass is also used instead of the metal material to reduce weight. Although the glass may be easily destroyed under tensile stress, the glass has extremely high strength with respect to compressive stress. Such features can be utilized when using the glass. It is discussed that a photomultiplier is incorporated in the pressure-resistant container made of glass in the thick ice of the Antarctic Continent for detecting elementary particles from space.
In addition, one of the great advantages of the glass is that the glass is transparent different from metal material and ceramic material. Because of this, the condition of the ocean floor and the deep sea can be visually observed by using the housed camera, video camera or the like.
Non-Patent Document 1 relates to prototype of a deep sea camera system using a pressure-resistant glass sphere. Non-Patent Document 1 describes that the glass sphere began to be used as the pressure-resistant container from around 1964 in America, however, there were problems of the state of the surface finishing, for example, thus, the pressure-resistant glass sphere was developed and tested with the cooperation of a Japanese glass manufacturer. Two kinds of glass spheres were developed and tested: one is the grass sphere having an outer diameter of 36 cm and an inner diameter of 32 cm; and the other is the grass sphere having an outer diameter of 36 cm and an inner diameter of 33 cm.
Non-Patent Document 2 describes a free-fall deep sea camera system using the glass sphere having an outer diameter of 36 cm and a thickness of 1.5 cm described in Non-Patent Document 1 and the glass sphere having an outer diameter of 26 cm and a thickness of 1 cm.
Patent Document 1 discloses a housing for a marine measuring instrument using a pair of glass-made hollow hemispherical bodies. However, two glass-made hollow hemispherical bodies are joined with each other via a protect cage without being directly in contact with each other at circular openings (ground joint surfaces).
Patent Document 2 points out that the technology of Patent Document 1 has problems of high material cost, high operation cost and low seal reliability by sealing. In order to improve the above described problems, Patent Document 2 discloses the technology of polishing the ground joint surfaces precisely (±4 μm), applying non-hardenable material on an equatorial plane joining portion which is located outside the ground joint surfaces, and covering the equatorial plane joining portion with an adhesive tape as a means for preventing the collapse caused by sea water invasion under high pressure in the deep sea.
Patent Document 3 discloses a pressure-resistant glass body formed by joining a pair of hollow hemispherical bodies at ground joint surfaces where the hollow hemispherical bodies are joined with each other by an adhesive bonding layer consisting of a curable adhesive agent applied to the ground joint surfaces. In the technology disclosed in Patent Document 2, the ground joint surfaces need to be polished precisely and there is a risk of positional deviation when two hollow hemispherical bodies are joined with each other. In order to prevent and solve the above described problems, two hollow hemispherical bodies are adhered with each other by the curable adhesive agent.
Patent Document 4 relates to a pressure-resistant structure formed by fitting a pair of glass-made hollow hemispherical bodies with each other at the ground joint surfaces, characterized in that a metal film is formed on at least one of the ground joint surfaces. In the technology disclosed in Patent Document 3, the ground joint surfaces are joined with each other by the adhesive bonding layer consisting of the curable adhesive agent. Because of this, when the pressure-resistant glass body is collected after the deep sea observation, the adhesive bonding layer should be destroyed to take out the housed observation apparatuses or the like. Thus, Patent Document 4 has a purpose to solve the problem that the pressure-resistant glass body can be used only once. Namely, Patent Document 4 advocates the merit that the observation apparatuses housed inside can be collected and the pressure-resistant structure can be repeatedly used without destroying the pressure-resistant structure after the deep sea observation by using the metal film instead of the adhesive bonding layer.
In addition, when the pressure-resistant structure is repeatedly used, the processes of pressurization (deep sea)→depressurization (ground)→pressurization→depressurization are repeated on the ground joint surfaces. Because of this, the ground joint surfaces are cracked or peeled. Patent Document 4 can solve the above described problem by reinforcing the ground joint surfaces with the metal film to prevent the occurrence of the crack and the peeling.
Patent Document 5 relates to an outer shell of a pressure-resistant container, a pressure-resistant container and an exploration apparatus, the pressure-resistant container being formed of ceramic and having a through hole. Patent Document 5 discloses the outer shell formed by a convex outer shell portion made of ceramic, characterized in that a thickness is large at a portion continuing from the outer shell portion and having the through hole in the thickness direction.
Non-Patent Document 3 is a technical specification of Floatation Glass Sphere for deep sea manufactured by Teledyne Benthos in U.S.A. The glass sphere having an outer diameter of 13 inch (33 cm), an inner diameter of 12 inch (30.5 cm), a weight of 9.07 kgf and a floating force of 10.4 kgf, and the glass sphere having an outer diameter of 17 inch (43.2 cm), an inner diameter of 15.9 inch (40.4 cm), a weight of 17.7 kgf and a floating force of 25.4 kgf are disclosed. Here, the floating force is a value obtained by subtracting the weight of the glass sphere from the buoyancy obtained by the glass sphere.
Patent Document 4 is a data sheet related to the glass sphere manufactured by Nautilus Marine Service GmbH in Germany. The glass sphere having an outer diameter of 17 inch (432 mm), a thickness of the spherical shell of 21 mm, 18 mm and 14 mm and the glass sphere having an outer diameter of 13 inch (330 mm) and a thickness of the spherical shell of 12 mm are disclosed, for example.
Patent Document 1: U.S. Pat. No. 3,563,089
Patent Document 2: U.S. Pat. No. 3,587,122
Patent Document 3: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2003-517571
Patent Document 4: Japanese Unexamined Patent Application Publication No. 2010-38854
Patent Document 5: Japanese patent No. 5313400
Non-Patent Document 1: About a test of a deep sea camera system using a pressure-resistant glass sphere, Report of Japan Marine Science and Technology Center No. 1, p. 26 to 31, 1977
Non-Patent Document 2: 4. Deep sea camera system including free-fall pressure-resistant glass sphere, JAMSTECTR 3, 1979
Non-Patent Document 3: http://teledynebenthos.com/product/flotation_instrument_housings/flotation-glass-spheres
Non-Patent Document 4: http://www.nautilus-gmbh.com/fileadmin/images_nautilus/002_VITROVEX/Instruments/Data_sheets/140101_VITROVEX_deep_sea_instrumentation_housings.pdf